transmission oil & fuel efficiency (MPG)?

[klancek]

Reading up (...and searching!...) on synthetic gear oil, transmission fluid, for my MT.

I saw this page which half way down talks about efficiency. I was wondering if it's legit.

The point: Has anyone using synthetic transmission fluid (redline, others, please say which one) noticed any change in miles per gallon? Also, please mention if you're stock or "off road"

[SD_GR]

The majority of efficiency loss in a vehicle's drivetrain results from friction generated in the differential gearing and manual transmission.

Probably true.

The special friction modifying characteristics of NEO 75W-90/RHD gear lubricant directly attacks this energy loss, therefore, substantially improving fuel economy.

Marketing, therefore worthless as a statement. Words like "special" are completely meaningless when trying to quantify an effect or result.

This has been documented by more than 6,000,000 mile of over-the-road testing in actual line haul truck service. The actual results proved an average reduction in fuel consumption in excess of 3% when compared to trucks using a conventionally formulated competitive quality gear oil. Additional testing in the laboratory and under controlled conditions on a test track substantiate the fuel economy increase of more that 3%.

.

Anecdotal (so it's your decision; for me, it's worthless, YMMV). They claim it has been "documented" but provide no references at all. For something to be "documented" I'd like to see peer-reviewed articles in established scientific journals. Anything else is just as likely to be a fairy tale as it is to be the honest truth, and there's no way of telling which is the case. If it's documented, it's not documented at the link you provided.

Also a heads up: They say the lube "provides" GL5 and GL6 performance. In English, this means exactly the opposite of what one might think: This is *not* a GL5 lube (!) but something they claim is "equivalent." A GL5 oil would say "GL5" plain and simple, and have something like an API listing etc. For warranty purposes, you need a GL5 oil (maybe an equivalent would do, check the wording in the manual.).

[klancek]

I agree about your evaluation of the link. You have to evalute marketing-ese carefully.

I'm really interested in people's gas milage--have you noticed any difference in your ride? Thanks

[SD_GR]

I use conventional gear lubes in the Impreza. In my AWD Mitsubishi I didn't notice any difference between conventional gear oil everywhere and Pennzoil synthetic GL5 in the gearbox/front and RedLine Shockproof in the transfer case and rear end. I drove mostly highway miles at roughly legal speeds.

[GV27]

I'm running Redline Shockproof Superlight which is probably the easiest flowing gear oil available and I noticed no difference. Not that the difference isn't there, just that if it is it's pretty small.